This invention relates to an image processing method and image processing apparatus capable of dodging or shutting light method, and in particular, to an image processing method and image processing apparatus capable of electronically making the image processing for dodging for the image data read by an image reading means.
In the case where a film (negative-film or positive-film) photographed in a condition with a large brightness difference is developed and printed on a photographic paper, it sometimes occurs that light portions present a uniformly white appearance losing a light tone (whitened or whitening) or dark portions present a uniformly black appearance losing a detailed tone (blackened or black fill-in).
In order to solve the above-mentioned problems of whitening and black fill-in, a technique called `dodging` or `burning-in` is sometimes used. The above-mentioned dodging and burning-in (hereinafter referred to as `dodging` inclusively in this specification) are the methods for obtaining a print without saturation in the light and dark portions, keeping a good contrast and gradation of each photographic object, by giving long time exposure selectively for the area considered to become uniformly white by using a shielding plate with a hole and giving short time exposure selectively for the area considered to become black fill-in by using a shielding plate, while giving usual exposure for the area of intermediate density. Further, in case of printing from a positive-film, a print without saturation can be obtained by the reversed operation of the above.
Furthermore, in the case where an electronic image processing is used, there are like problems of uniform whitening and black fill-in in the final print too; hence, a method for eliminating the uniform whitening and black fill-in by compressing the dynamic range of the original image (described in Japanese laid open patent H9-182093), a method for eliminating the whitening and fill-in by carrying out the dodging image processing preparing a dodging mask from the original (described in Japanese laid open patent H9-18704), and so forth have been proposed.
In the method described in the Japanese laid open patent H9-182093 to compress the dynamic range, it is produced the problem that the contrast and gradation of each photographic object can not be reproduced because the dynamic range is wholly compressed.
Further, in the method described in the Japanese laid open patent H9-18704 to carry out dodging by preparing a dodging mask, the proper effect of dodging is also not to be obtained like the method described in the Japanese laid open patent H9-182093, because the original is subjected to low-pass filter processing and then a dodging mask having a gradation compressed by a gradation-compressing LUT is applied together with the original image.
Furthermore, in some cases of electronic image processing, soft focusing is practiced. In these cases, in order to obtain a soft focus image with an appearance of blurred light as obtained by using a soft filter at the time of photographing, it is required to superpose a mask image with respect to respective numerical values corresponding to the brightness (energy quantity E) at the time of photographing.
On the other hand, in a general print system, it is favorable that the image data is handled in a unit system wherein the higher brightness domain is compressed such as density and L*, in order to secure a sufficient range of gradation reproduction and the precision of image processing.
For this reason, in order to obtain a favorable soft focus image, an additional processing such as converting density or L* into E.fwdarw.composing processing.fwdarw.converting E into density or L*; hence, the load for the computer is increased owing to the necessity to keep the precision of processing high and the increase of the amount of calculation process.
Further, as another means for obtaining soft focus effect, a soft focus processing to be made at the time of printing can also be available; it is characterized by obtaining a print of a spread color, and in low key. In this case too, it can not be actualized by merely blending the image data values corresponding to density or L*, but it requires the calculation process such as converting density or L* into print exposure quantity E'.fwdarw.composing processing.fwdarw.converting E' into density or L*, resulting in a heavy load like the soft focus processing of the type made at the time of photographing.
Furthermore, in order to obtain the soft focus effect, it is necessary to carry out a blurring filter processing of enough size; hence, it gives a large burden to the image processing system, making a high-speed processing difficult.